Electron discharge device and improved anode therefor



' Sept. 3, 1935. w G MORAN 2,013,419

ELECTRON DISCHARGE DEVICE AND IMPROVED ANODE THEREFOR Filed July 15,1953 INVENTOR W 6. MOP/71V ATTDRNE Patented Sept. 3, 1935 PATENT OFFICEELECTRON DISCHARGE DEVICE AND IMPROVED ANODE THEREFOR William G. Moran,Bloomfield, N. J., assignor to Westinghouse Lamp Company, a corporationof Pennsylvania Application July 15, 1933, Serial No. 680,515

13 Claims.

This invention relates to electric discharge devices and moreparticularly to an improved type of anode therefor. In its more specificaspect the invention is an improvement of the electron discharge deviceand anode disclosed in the United States application of George M.Dinnick, Serial No. 673,865, filed June 1, 1933, and assigned to thesame assignee as the present invention. Said application discloses athree-electrode tube 1 including a grid, an anode and a cathode. Theanode comprises a single unitary piece of graphite in the form ofahollow tubular element. The anode surrounds both the grid and filament.

Although tubes containing an anode of .the above character have beenanadvance in the art, it was found that some of the tubes were faulty. Inthe course of my work with these tubes I found that in many cases theshortcomings of these faulty tubes was attributable to the anode. Duringthe normal operation of the tube some of the graphite was loosened fromthe plate and was transferred in the form of, a loose dustrto the gridand filament, This graphite then formed a thin coating or film on thegrid and cathode. 25 The coating or film of graphite on the filamentarycathode increased the thermal emissivity of the filament. Sometimes theincrease in the thermal emissivity of the cathode would cause thereduction of the filament temperature to a value below the necessaryoperating value at normal filament voltage and current.

In order to obviate this difficulty, I have employed a simple expedientwhich consists in the employment of a material on the anode to entrapany loose dust particles and which will prevent graphite particles frombecoming loosened from the anode and being deposited on the filament orgrid.

An object of my invention is to provide an improved electric dischargedevice.

Another object of my invention is to provide an electric dischargedevice which, during seasoning or normal operations thereof, will notcause an increase of the thermal emissivity of the cathode.

A further object of my invention is to provide an electric dischargedevice having a graphite anode and which may be seasoned or operatedunder normal conditions without coating the filament thereof with a filmof carbon.

A still further object of my invention is to provide a graphite anodehaving a protective surface thereon; V

Other objects and advantages of my invention will be readily apparentfrom the following description and drawing wherein:

Figure 1 represents a longitudinal front view, with some of the partsbroken away, of a discharge device embodying my invention;

Figure 2 represents a perspective view of an anode embodying myinvention; and

Figure 3 represents a horizontal cross sectional view of Figure 2 takenat about the mid-length thereof.

The electric discharge device, with the exception of the anode, is thesame as that illustrated in the above mentioned application. As shown,it comprises an envelope 9 having a re-entrant tube In extendingtherein. The re-entrant stem 10 has a press in which are secured aplurality of spaced conductors [2, I3 and I4 extending interiorly andexteriorly of said envelope.

A flexible metallic band 15 is wrapped around the-stem l0 below thepress thereof and is in frictional engagement therewith by means of anut and bolt arrangement It. At one side of said press are a pluralityof standards H and I8 which are welded to said band [5 and extendupwardly in said envelope. A corresponding pair of standards are securedto said band at the other side of the press. The standards I! and 18 arewelded to each other at that position where the standard l8 terminates.The standard I1 has the major portion thereof extending upwardly in saidenvelope and substantially parallel to the longitudinal axis thereof anappreciable distance above the upper limit of the standard [8.

A cruciform insulator 19, having diametrically disposed openings in oneof the cross arms thereof, has the upper portion of the standards I 1extending through these openings with said cross arm resting upon theupper limit of the standards l8. The other cross arm of the insulator l9has a plurality of openings therein adapted to accommodate conductorsand supports 29, 2|, 22 and 23. A suitably sized wire 24 is wound aroundand secured to the conductors 20 and 23 to serve as the grid element. Aninverted M-shaped filament 25 serves as the cathode element. Thefilament 25 has its lower bight secured to a conductor, not shown, andits upper bights secured to a pair of hooks 2B and 21. The ends of thefilament 25 are secured to conductors 2| and 22. A small carbon shallowdisc 28, having a circular opening therein, is mounted on each of thestandards IT.

A rigid improved anode 29 surrounds the grid and filament. The main bodyfoundation or base of the anode includes a hollow elongated memberconsisting of two flat sides 30 of sufficient width and arrangedparallel to each other and integral with two curved portions 3! formingthe other sides. A cross sectional View of said anode, which is in theform of a hollow shell, at right angles to its major axis, is in theform of a rectangle having rounded ends. At the midwidth of each of saidflat sides and extending along the entire length thereof are outwardlyextending lateral extensions 32. Each extension 32 is of appreciablecross-sectional area and has an opening therein throughout the entirelength thereof. The opening may be cylindrical, as shown, or in the formof a groove.

The main body of the anode, as above described, is a unitary singleelement composed of graphite or the like. Because of its composition,the anode has a good heat emissivity characteristic, comparable withthat of a black body, which is a desirable feature in an anodeconstruction employed in radio tubes. In order that the filament as wellas the grid may be protected from being covered with a film of carbonfrom the anode and so that the anode may still retain itsheat-emissivity characteristic, I coat the entire interior surface ofthe anode with a metal such as copper, nickel, iron, chromium,molybdenum, tungsten, platinum or the like. If desired, I may also coatthe upper and lower extreme faces of the body of the anode with one ofthe above metals.

The coating, designated as 33, is in the form of a thin film which maybedeposited thereon in any suitable manner, as for example,electrodeposition, an oxide paste, deposit and subsequently reducedthereon or by other convenient means. The metal coating 33 is inintimate contact with and serves to coat that portion of the anode whichis to be subjected to bombardment so that no graphite dust may be formedand/or transferred to the grid and filament. The coating is firmlyadherent to and supported by the anode body and is substantiallyimpervious to any graphite dust that may have been on, the inner surfacethereof prior to coating. By limiting the area of coating to only theinterior surface and the extreme upper and lower faces of the anode, theheat radiating properties of the effective heat radiating surface of theanode remains unimpaired. V The coated anode may be readily assembled inan electric device by simply sliding the standards I! through thelongitudinally disposed openings in the extensions 32 of the anode. Thediameter of the openings is substantially the same as that of thestandards I1. Small shallow discs 35, the same type as the discsheretofore described, have openings therein through which the upperportions of the standards ll extend so that these discs rest upon thelateral extensions of the anode. A cruciform insulator 36, similar tothe insulator l9, also has openings therein adapted to accommodate thestandards I'lwhich project therethrough and extend upwardly thereabove.

The insulator 36 has openings adapted to receive conductors 2B and 23which extend there-.

through. Short cross-bars 31 are welded to the upper portion of theconductor 20 immediately adjacent and above the insulator 36. Acrossbar37 is also welded to the lower portion of the conductor 23 immediatelyadjacent and below the insulator l9. Hooks 26 and 27, which support theupper bights of the filament, have the shanks thereof integral withsprings which rest in small recesses in the upper face of v theinsulator 36,

with the shanks thereof extending through openings in said insulators.

Resting upon the insulator 36 and adjacent the outer portions thereofand welded to each of the standards I? above the insulator, is an.inverted U-shaped rod 38 having the sides thereof welded to thestandards I! and [8 at the places where the sides of said U-shapedrodsand standards ode having the foundation portion thereof composed of amaterial having a relatively high heat emissivity characteristic, ametallic coating on that surface of the anode which is bombarded by theelectronsemanating from the cathode duringthe operation of the device.

2. An electric device comprising an envelope, an anode andacathode,therein, said anode hav ing a foundation composedof graphite, a metallic coating located on that surface of said foundation which. isbombarded by. the electrons from the cathode during. seasoning ornormaloperation of the device. 7 j V 3. An electric device comprisingan. envelope,-

ing a portion of the area thereof facing said an anode and a cathodetherein, saidanode hava cathode and a portion of the area thereof facingsaid envelope, said anode being composed essen tially of graphite, ametallicv coating on said first mentioned portion, said other portionbeing substantially uncoated. 1 1

4. An electric device comprising an envelope, an anodeand a cathodetherein, said-cathode having a'foundation composed of graphite, a

coating of nickel forming the interior surface of said anode whichsurface is normally bombarded bythe electrons from the cathode duringthe seasoning or commercial operation of said device.

5. An electric discharge device comprising an envelope, an anode and acathode therein, said anode surrounding said cathode, the foundation ofsaid anode being composed of a material hav-= ing a. highheat-emissivity characteristic comparable: with that of a black body, .ametallic coating; locatedon the interior surface of said foundation. I

,6. An electric device comprising, an, envelope, an anode and a cathodetherein, the foundation of said anode being composed of graphite, saidanode surrounding said cathode, a high melting point metal coating onthe interior surface .of

said anode. r

7. An electric device comprising an envelope,

an anode and a cathode therein, said anode being, a hollow body andsurrounding said cathode,

the foundation of said anode being composed of. 7'

graphitaa coating of nickel on the interior surface of said anode.

8. An electric device comprising an envelope, an anode and a cathodetherein, said anode being a hollow body and surrounding said: cathode,the foundation of said anodebeing, composed of graphite, a metalliccoating located on the interior surface of said anode.

9. An electric device comprising an envelope, an anode and a cathodetherein, said anode partially surrounding said cathode and beingcomposed of graphite, a relatively thin film of metal coating theinterior surface of said anode to prevent the graphite of the anode frombeing deposited onto the cathode during bombardment of said anode.

10. A radio tube including an anode, a cathode and a grid, said gridsurrounding said anode, said anode surrounding said grid, said anodebeing composed of carbon, a metallic coating on the surface thereoffacing said grid, the major portion of the remaining surface beingsubstantially uncoated.

11. An electric device including an anode, a cathode and a grid, saidgrid surrounding said anode, said anode surrounding said grid, saidanode being tubular .and composed of carbon, a metallic coating on theinterior surface thereof and the exterior surface thereof beingsubstantially uncoated.

12. An anode comprising a base and a metallic coating secured toaportion of the surface of the base, the remainder of the base beingsubstantially uncoated, said base being composed of graphite, said firstmentioned portion being that portion which is to be bombarded when theanode is employed in a discharge device.

13. An electric device comprising an anode and a cathode therein, saidanode comprising a foundation of carbon, a metallic film locatedsubstantially on only that portion of the surface of said foundationwhich is to be subjected to electron bombardment.

WILLIAM G. MORAN.

